Stimulation Techniques in Epilepsy: How Do We Choose?
APRIL 10, 2019
MD Magazine Staff
Michael R. Sperling, MD: Lots of other interesting things are coming up for treatment too. So we have now a variety of stimulation devices, or lessened days of surgery. Where do you think about employing stimulation? And how do you think about it, in terms of what its efficacy is, Kate?
Kathryn A. Davis, MD, MS, FAES: Sure. So again, similar to what Trevor said, that first step is really identifying and defining intractable epilepsy. And if a patient has intractable generalized epilepsy, the only device that currently is approved is the vagal nerve stimulation [VNS]. The vast majority of patients, as we discussed at the beginning, have focal epilepsies, and if they have intractable focal epilepsy, the first thing I think of to do is to evaluate them for potential surgery, either a resective surgery or now laser ablation, which is becoming increasing popular as a less invasive option for a potential cure.
And the patients for whom I consider other types of stimulation, mainly deep brain stimulation or responsive nerve stimulation, and NeuroPace RNS device, are patients who are not excellent candidates for a potentially curative surgery in almost all cases, and that may be because of their eloquent cortex, multifocal disease, or poorly localized disease, etc.
Michael R. Sperling, MD: Yes, it’s important to remember with the stimulation that you’re talking palliation because I’m not talking about it being seizures. It’s entirely different to say, “Well, I’ll try stimulator rather than removing something,” your end point is quite different.
On the other hand, as you mentioned, I think we found too that the stereotactic laser interstitial thermal ablation is something that we’re doing more of. We’ve had quite a few patients who would not have considered surgery before who are now willing to do that because they’re in and out of the hospital in 24 hours, and we do surgery on Friday, they go home Saturday, and they’re back to work on Monday. And I’ve had more than 1 patient tell me on the day that they went home, they went to the mall to shop they felt so well. Has that affected your pediatric practice as much? And I’m wondering, too, about hypothalamic hamartomas.
Trevor J. Resnick, MD: Well, we’ve been doing focus beam ultrasound as well for hypothalamic hamartomas, which is totally noninvasive. But the FDA is only allowing us to do it in certain populations. But absolutely, the laser ablation is exactly the scenario you’re talking about. And sometimes the scenario is that it’s resective surgery in that patient who had a higher likelihood of success. But you end up doing laser ablation, even though you may not be getting the entire epileptogenic zone because it’s less invasive. So your success rate may end up not looking as good, but the procedure is so much better tolerated. And that’s often a discussion we end up having.
Michael R. Sperling, MD: And what is your experience in terms of patient compliance with some of these stimulation techniques? The data have to be downloaded, patients have to come back frequently. Has that been a significant issue, or do you think patients are reasonably compliant, by and large?
Jesus E. Pina-Garza, MD: Well, in general, there’s 1 thing that takes adherence away. So you have a programming device. The only thing that, in some cases, is running out of battery. So you have frequent monitoring; you can detect that. But it’s 1 of the advantages, I think, in the case of vagal nerve stimulation. The question was never answered, what would I do for a naïve patient? But it would be very attractive to not have to deal with toxicity or problems with adherence if your work is good to pharmacological management. We’ll never have that answer.
But for the refractory patients, some of the advantages of having a potential benefit of mood, having a faster recovery postictally, make a huge difference for some of those patients. So there are things that you can appreciate for the more effective patients. And so the laser ablation is incredibly better accepted and tolerated because it’s a less invasive procedure.
Michael R. Sperling, MD: So within this menu of stimulation, is there a rational way to decide if someone is a better candidate for 1 type than another? We can do external stimulation at the vagus nerves, internal with responsive neurostimulation, internal with deep brain stimulation, and a variety of other things that are being investigated. Is there a sensible way to make a decision now? Do you have an algorithm that you use? Or is it still in need of further development?
Kathryn A. Davis, MD, MS, FAES: I definitely think it’s the latter, that we as a field need better biomarkers to tell us which of these devices to use. We’re at a place where we’re deciding which of these 3 currently FDA-approved devices is best for our patient. We don’t have an algorithm. I have an internal algorithm. The devices, the intracranial devices work about as well as one another—at least they weren’t compared head-to-head, similar to the drugs—but some of the adverse-effect profiles differ, and that could play a role. For instance, a patient with significant psychiatric comorbidity may be more appropriate for the RNS device rather than deep brain stimulation based on the data that we have right now. And the vagal nerve stimulation likely works a little less well than these other devices, but it’s much less invasive. Another issue with the RNS device is that it is more complex for the patient. And in the adult population, that can play a role in whether we think the patient has the ability to, as Mike was saying, download the data at home to the laptop and really, appropriately, use the device so that we can program it. That issue is not there with deep brain stimulation or the vagal nerve stimulator.
Michael R. Sperling, MD: What’s impressed me is that with both deep brain simulation and responsive neurostimulation, a percentage of patients have extended seizure-free periods. Unfortunately, we don’t have data on VNS to know whether that happens as well, but that is somewhat hopeful.
Transcript edited for clarity.